xref: /linux/security/keys/keyctl.c (revision b889fcf63cb62e7fdb7816565e28f44dbe4a76a5)
1 /* Userspace key control operations
2  *
3  * Copyright (C) 2004-5 Red Hat, Inc. All Rights Reserved.
4  * Written by David Howells (dhowells@redhat.com)
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License
8  * as published by the Free Software Foundation; either version
9  * 2 of the License, or (at your option) any later version.
10  */
11 
12 #include <linux/module.h>
13 #include <linux/init.h>
14 #include <linux/sched.h>
15 #include <linux/slab.h>
16 #include <linux/syscalls.h>
17 #include <linux/key.h>
18 #include <linux/keyctl.h>
19 #include <linux/fs.h>
20 #include <linux/capability.h>
21 #include <linux/string.h>
22 #include <linux/err.h>
23 #include <linux/vmalloc.h>
24 #include <linux/security.h>
25 #include <asm/uaccess.h>
26 #include "internal.h"
27 
28 static int key_get_type_from_user(char *type,
29 				  const char __user *_type,
30 				  unsigned len)
31 {
32 	int ret;
33 
34 	ret = strncpy_from_user(type, _type, len);
35 	if (ret < 0)
36 		return ret;
37 	if (ret == 0 || ret >= len)
38 		return -EINVAL;
39 	if (type[0] == '.')
40 		return -EPERM;
41 	type[len - 1] = '\0';
42 	return 0;
43 }
44 
45 /*
46  * Extract the description of a new key from userspace and either add it as a
47  * new key to the specified keyring or update a matching key in that keyring.
48  *
49  * If the description is NULL or an empty string, the key type is asked to
50  * generate one from the payload.
51  *
52  * The keyring must be writable so that we can attach the key to it.
53  *
54  * If successful, the new key's serial number is returned, otherwise an error
55  * code is returned.
56  */
57 SYSCALL_DEFINE5(add_key, const char __user *, _type,
58 		const char __user *, _description,
59 		const void __user *, _payload,
60 		size_t, plen,
61 		key_serial_t, ringid)
62 {
63 	key_ref_t keyring_ref, key_ref;
64 	char type[32], *description;
65 	void *payload;
66 	long ret;
67 	bool vm;
68 
69 	ret = -EINVAL;
70 	if (plen > 1024 * 1024 - 1)
71 		goto error;
72 
73 	/* draw all the data into kernel space */
74 	ret = key_get_type_from_user(type, _type, sizeof(type));
75 	if (ret < 0)
76 		goto error;
77 
78 	description = NULL;
79 	if (_description) {
80 		description = strndup_user(_description, PAGE_SIZE);
81 		if (IS_ERR(description)) {
82 			ret = PTR_ERR(description);
83 			goto error;
84 		}
85 		if (!*description) {
86 			kfree(description);
87 			description = NULL;
88 		}
89 	}
90 
91 	/* pull the payload in if one was supplied */
92 	payload = NULL;
93 
94 	vm = false;
95 	if (_payload) {
96 		ret = -ENOMEM;
97 		payload = kmalloc(plen, GFP_KERNEL | __GFP_NOWARN);
98 		if (!payload) {
99 			if (plen <= PAGE_SIZE)
100 				goto error2;
101 			vm = true;
102 			payload = vmalloc(plen);
103 			if (!payload)
104 				goto error2;
105 		}
106 
107 		ret = -EFAULT;
108 		if (copy_from_user(payload, _payload, plen) != 0)
109 			goto error3;
110 	}
111 
112 	/* find the target keyring (which must be writable) */
113 	keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
114 	if (IS_ERR(keyring_ref)) {
115 		ret = PTR_ERR(keyring_ref);
116 		goto error3;
117 	}
118 
119 	/* create or update the requested key and add it to the target
120 	 * keyring */
121 	key_ref = key_create_or_update(keyring_ref, type, description,
122 				       payload, plen, KEY_PERM_UNDEF,
123 				       KEY_ALLOC_IN_QUOTA);
124 	if (!IS_ERR(key_ref)) {
125 		ret = key_ref_to_ptr(key_ref)->serial;
126 		key_ref_put(key_ref);
127 	}
128 	else {
129 		ret = PTR_ERR(key_ref);
130 	}
131 
132 	key_ref_put(keyring_ref);
133  error3:
134 	if (!vm)
135 		kfree(payload);
136 	else
137 		vfree(payload);
138  error2:
139 	kfree(description);
140  error:
141 	return ret;
142 }
143 
144 /*
145  * Search the process keyrings and keyring trees linked from those for a
146  * matching key.  Keyrings must have appropriate Search permission to be
147  * searched.
148  *
149  * If a key is found, it will be attached to the destination keyring if there's
150  * one specified and the serial number of the key will be returned.
151  *
152  * If no key is found, /sbin/request-key will be invoked if _callout_info is
153  * non-NULL in an attempt to create a key.  The _callout_info string will be
154  * passed to /sbin/request-key to aid with completing the request.  If the
155  * _callout_info string is "" then it will be changed to "-".
156  */
157 SYSCALL_DEFINE4(request_key, const char __user *, _type,
158 		const char __user *, _description,
159 		const char __user *, _callout_info,
160 		key_serial_t, destringid)
161 {
162 	struct key_type *ktype;
163 	struct key *key;
164 	key_ref_t dest_ref;
165 	size_t callout_len;
166 	char type[32], *description, *callout_info;
167 	long ret;
168 
169 	/* pull the type into kernel space */
170 	ret = key_get_type_from_user(type, _type, sizeof(type));
171 	if (ret < 0)
172 		goto error;
173 
174 	/* pull the description into kernel space */
175 	description = strndup_user(_description, PAGE_SIZE);
176 	if (IS_ERR(description)) {
177 		ret = PTR_ERR(description);
178 		goto error;
179 	}
180 
181 	/* pull the callout info into kernel space */
182 	callout_info = NULL;
183 	callout_len = 0;
184 	if (_callout_info) {
185 		callout_info = strndup_user(_callout_info, PAGE_SIZE);
186 		if (IS_ERR(callout_info)) {
187 			ret = PTR_ERR(callout_info);
188 			goto error2;
189 		}
190 		callout_len = strlen(callout_info);
191 	}
192 
193 	/* get the destination keyring if specified */
194 	dest_ref = NULL;
195 	if (destringid) {
196 		dest_ref = lookup_user_key(destringid, KEY_LOOKUP_CREATE,
197 					   KEY_WRITE);
198 		if (IS_ERR(dest_ref)) {
199 			ret = PTR_ERR(dest_ref);
200 			goto error3;
201 		}
202 	}
203 
204 	/* find the key type */
205 	ktype = key_type_lookup(type);
206 	if (IS_ERR(ktype)) {
207 		ret = PTR_ERR(ktype);
208 		goto error4;
209 	}
210 
211 	/* do the search */
212 	key = request_key_and_link(ktype, description, callout_info,
213 				   callout_len, NULL, key_ref_to_ptr(dest_ref),
214 				   KEY_ALLOC_IN_QUOTA);
215 	if (IS_ERR(key)) {
216 		ret = PTR_ERR(key);
217 		goto error5;
218 	}
219 
220 	/* wait for the key to finish being constructed */
221 	ret = wait_for_key_construction(key, 1);
222 	if (ret < 0)
223 		goto error6;
224 
225 	ret = key->serial;
226 
227 error6:
228  	key_put(key);
229 error5:
230 	key_type_put(ktype);
231 error4:
232 	key_ref_put(dest_ref);
233 error3:
234 	kfree(callout_info);
235 error2:
236 	kfree(description);
237 error:
238 	return ret;
239 }
240 
241 /*
242  * Get the ID of the specified process keyring.
243  *
244  * The requested keyring must have search permission to be found.
245  *
246  * If successful, the ID of the requested keyring will be returned.
247  */
248 long keyctl_get_keyring_ID(key_serial_t id, int create)
249 {
250 	key_ref_t key_ref;
251 	unsigned long lflags;
252 	long ret;
253 
254 	lflags = create ? KEY_LOOKUP_CREATE : 0;
255 	key_ref = lookup_user_key(id, lflags, KEY_SEARCH);
256 	if (IS_ERR(key_ref)) {
257 		ret = PTR_ERR(key_ref);
258 		goto error;
259 	}
260 
261 	ret = key_ref_to_ptr(key_ref)->serial;
262 	key_ref_put(key_ref);
263 error:
264 	return ret;
265 }
266 
267 /*
268  * Join a (named) session keyring.
269  *
270  * Create and join an anonymous session keyring or join a named session
271  * keyring, creating it if necessary.  A named session keyring must have Search
272  * permission for it to be joined.  Session keyrings without this permit will
273  * be skipped over.
274  *
275  * If successful, the ID of the joined session keyring will be returned.
276  */
277 long keyctl_join_session_keyring(const char __user *_name)
278 {
279 	char *name;
280 	long ret;
281 
282 	/* fetch the name from userspace */
283 	name = NULL;
284 	if (_name) {
285 		name = strndup_user(_name, PAGE_SIZE);
286 		if (IS_ERR(name)) {
287 			ret = PTR_ERR(name);
288 			goto error;
289 		}
290 	}
291 
292 	/* join the session */
293 	ret = join_session_keyring(name);
294 	kfree(name);
295 
296 error:
297 	return ret;
298 }
299 
300 /*
301  * Update a key's data payload from the given data.
302  *
303  * The key must grant the caller Write permission and the key type must support
304  * updating for this to work.  A negative key can be positively instantiated
305  * with this call.
306  *
307  * If successful, 0 will be returned.  If the key type does not support
308  * updating, then -EOPNOTSUPP will be returned.
309  */
310 long keyctl_update_key(key_serial_t id,
311 		       const void __user *_payload,
312 		       size_t plen)
313 {
314 	key_ref_t key_ref;
315 	void *payload;
316 	long ret;
317 
318 	ret = -EINVAL;
319 	if (plen > PAGE_SIZE)
320 		goto error;
321 
322 	/* pull the payload in if one was supplied */
323 	payload = NULL;
324 	if (_payload) {
325 		ret = -ENOMEM;
326 		payload = kmalloc(plen, GFP_KERNEL);
327 		if (!payload)
328 			goto error;
329 
330 		ret = -EFAULT;
331 		if (copy_from_user(payload, _payload, plen) != 0)
332 			goto error2;
333 	}
334 
335 	/* find the target key (which must be writable) */
336 	key_ref = lookup_user_key(id, 0, KEY_WRITE);
337 	if (IS_ERR(key_ref)) {
338 		ret = PTR_ERR(key_ref);
339 		goto error2;
340 	}
341 
342 	/* update the key */
343 	ret = key_update(key_ref, payload, plen);
344 
345 	key_ref_put(key_ref);
346 error2:
347 	kfree(payload);
348 error:
349 	return ret;
350 }
351 
352 /*
353  * Revoke a key.
354  *
355  * The key must be grant the caller Write or Setattr permission for this to
356  * work.  The key type should give up its quota claim when revoked.  The key
357  * and any links to the key will be automatically garbage collected after a
358  * certain amount of time (/proc/sys/kernel/keys/gc_delay).
359  *
360  * If successful, 0 is returned.
361  */
362 long keyctl_revoke_key(key_serial_t id)
363 {
364 	key_ref_t key_ref;
365 	long ret;
366 
367 	key_ref = lookup_user_key(id, 0, KEY_WRITE);
368 	if (IS_ERR(key_ref)) {
369 		ret = PTR_ERR(key_ref);
370 		if (ret != -EACCES)
371 			goto error;
372 		key_ref = lookup_user_key(id, 0, KEY_SETATTR);
373 		if (IS_ERR(key_ref)) {
374 			ret = PTR_ERR(key_ref);
375 			goto error;
376 		}
377 	}
378 
379 	key_revoke(key_ref_to_ptr(key_ref));
380 	ret = 0;
381 
382 	key_ref_put(key_ref);
383 error:
384 	return ret;
385 }
386 
387 /*
388  * Invalidate a key.
389  *
390  * The key must be grant the caller Invalidate permission for this to work.
391  * The key and any links to the key will be automatically garbage collected
392  * immediately.
393  *
394  * If successful, 0 is returned.
395  */
396 long keyctl_invalidate_key(key_serial_t id)
397 {
398 	key_ref_t key_ref;
399 	long ret;
400 
401 	kenter("%d", id);
402 
403 	key_ref = lookup_user_key(id, 0, KEY_SEARCH);
404 	if (IS_ERR(key_ref)) {
405 		ret = PTR_ERR(key_ref);
406 		goto error;
407 	}
408 
409 	key_invalidate(key_ref_to_ptr(key_ref));
410 	ret = 0;
411 
412 	key_ref_put(key_ref);
413 error:
414 	kleave(" = %ld", ret);
415 	return ret;
416 }
417 
418 /*
419  * Clear the specified keyring, creating an empty process keyring if one of the
420  * special keyring IDs is used.
421  *
422  * The keyring must grant the caller Write permission for this to work.  If
423  * successful, 0 will be returned.
424  */
425 long keyctl_keyring_clear(key_serial_t ringid)
426 {
427 	key_ref_t keyring_ref;
428 	long ret;
429 
430 	keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
431 	if (IS_ERR(keyring_ref)) {
432 		ret = PTR_ERR(keyring_ref);
433 
434 		/* Root is permitted to invalidate certain special keyrings */
435 		if (capable(CAP_SYS_ADMIN)) {
436 			keyring_ref = lookup_user_key(ringid, 0, 0);
437 			if (IS_ERR(keyring_ref))
438 				goto error;
439 			if (test_bit(KEY_FLAG_ROOT_CAN_CLEAR,
440 				     &key_ref_to_ptr(keyring_ref)->flags))
441 				goto clear;
442 			goto error_put;
443 		}
444 
445 		goto error;
446 	}
447 
448 clear:
449 	ret = keyring_clear(key_ref_to_ptr(keyring_ref));
450 error_put:
451 	key_ref_put(keyring_ref);
452 error:
453 	return ret;
454 }
455 
456 /*
457  * Create a link from a keyring to a key if there's no matching key in the
458  * keyring, otherwise replace the link to the matching key with a link to the
459  * new key.
460  *
461  * The key must grant the caller Link permission and the the keyring must grant
462  * the caller Write permission.  Furthermore, if an additional link is created,
463  * the keyring's quota will be extended.
464  *
465  * If successful, 0 will be returned.
466  */
467 long keyctl_keyring_link(key_serial_t id, key_serial_t ringid)
468 {
469 	key_ref_t keyring_ref, key_ref;
470 	long ret;
471 
472 	keyring_ref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
473 	if (IS_ERR(keyring_ref)) {
474 		ret = PTR_ERR(keyring_ref);
475 		goto error;
476 	}
477 
478 	key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE, KEY_LINK);
479 	if (IS_ERR(key_ref)) {
480 		ret = PTR_ERR(key_ref);
481 		goto error2;
482 	}
483 
484 	ret = key_link(key_ref_to_ptr(keyring_ref), key_ref_to_ptr(key_ref));
485 
486 	key_ref_put(key_ref);
487 error2:
488 	key_ref_put(keyring_ref);
489 error:
490 	return ret;
491 }
492 
493 /*
494  * Unlink a key from a keyring.
495  *
496  * The keyring must grant the caller Write permission for this to work; the key
497  * itself need not grant the caller anything.  If the last link to a key is
498  * removed then that key will be scheduled for destruction.
499  *
500  * If successful, 0 will be returned.
501  */
502 long keyctl_keyring_unlink(key_serial_t id, key_serial_t ringid)
503 {
504 	key_ref_t keyring_ref, key_ref;
505 	long ret;
506 
507 	keyring_ref = lookup_user_key(ringid, 0, KEY_WRITE);
508 	if (IS_ERR(keyring_ref)) {
509 		ret = PTR_ERR(keyring_ref);
510 		goto error;
511 	}
512 
513 	key_ref = lookup_user_key(id, KEY_LOOKUP_FOR_UNLINK, 0);
514 	if (IS_ERR(key_ref)) {
515 		ret = PTR_ERR(key_ref);
516 		goto error2;
517 	}
518 
519 	ret = key_unlink(key_ref_to_ptr(keyring_ref), key_ref_to_ptr(key_ref));
520 
521 	key_ref_put(key_ref);
522 error2:
523 	key_ref_put(keyring_ref);
524 error:
525 	return ret;
526 }
527 
528 /*
529  * Return a description of a key to userspace.
530  *
531  * The key must grant the caller View permission for this to work.
532  *
533  * If there's a buffer, we place up to buflen bytes of data into it formatted
534  * in the following way:
535  *
536  *	type;uid;gid;perm;description<NUL>
537  *
538  * If successful, we return the amount of description available, irrespective
539  * of how much we may have copied into the buffer.
540  */
541 long keyctl_describe_key(key_serial_t keyid,
542 			 char __user *buffer,
543 			 size_t buflen)
544 {
545 	struct key *key, *instkey;
546 	key_ref_t key_ref;
547 	char *tmpbuf;
548 	long ret;
549 
550 	key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_VIEW);
551 	if (IS_ERR(key_ref)) {
552 		/* viewing a key under construction is permitted if we have the
553 		 * authorisation token handy */
554 		if (PTR_ERR(key_ref) == -EACCES) {
555 			instkey = key_get_instantiation_authkey(keyid);
556 			if (!IS_ERR(instkey)) {
557 				key_put(instkey);
558 				key_ref = lookup_user_key(keyid,
559 							  KEY_LOOKUP_PARTIAL,
560 							  0);
561 				if (!IS_ERR(key_ref))
562 					goto okay;
563 			}
564 		}
565 
566 		ret = PTR_ERR(key_ref);
567 		goto error;
568 	}
569 
570 okay:
571 	/* calculate how much description we're going to return */
572 	ret = -ENOMEM;
573 	tmpbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
574 	if (!tmpbuf)
575 		goto error2;
576 
577 	key = key_ref_to_ptr(key_ref);
578 
579 	ret = snprintf(tmpbuf, PAGE_SIZE - 1,
580 		       "%s;%d;%d;%08x;%s",
581 		       key->type->name,
582 		       from_kuid_munged(current_user_ns(), key->uid),
583 		       from_kgid_munged(current_user_ns(), key->gid),
584 		       key->perm,
585 		       key->description ?: "");
586 
587 	/* include a NUL char at the end of the data */
588 	if (ret > PAGE_SIZE - 1)
589 		ret = PAGE_SIZE - 1;
590 	tmpbuf[ret] = 0;
591 	ret++;
592 
593 	/* consider returning the data */
594 	if (buffer && buflen > 0) {
595 		if (buflen > ret)
596 			buflen = ret;
597 
598 		if (copy_to_user(buffer, tmpbuf, buflen) != 0)
599 			ret = -EFAULT;
600 	}
601 
602 	kfree(tmpbuf);
603 error2:
604 	key_ref_put(key_ref);
605 error:
606 	return ret;
607 }
608 
609 /*
610  * Search the specified keyring and any keyrings it links to for a matching
611  * key.  Only keyrings that grant the caller Search permission will be searched
612  * (this includes the starting keyring).  Only keys with Search permission can
613  * be found.
614  *
615  * If successful, the found key will be linked to the destination keyring if
616  * supplied and the key has Link permission, and the found key ID will be
617  * returned.
618  */
619 long keyctl_keyring_search(key_serial_t ringid,
620 			   const char __user *_type,
621 			   const char __user *_description,
622 			   key_serial_t destringid)
623 {
624 	struct key_type *ktype;
625 	key_ref_t keyring_ref, key_ref, dest_ref;
626 	char type[32], *description;
627 	long ret;
628 
629 	/* pull the type and description into kernel space */
630 	ret = key_get_type_from_user(type, _type, sizeof(type));
631 	if (ret < 0)
632 		goto error;
633 
634 	description = strndup_user(_description, PAGE_SIZE);
635 	if (IS_ERR(description)) {
636 		ret = PTR_ERR(description);
637 		goto error;
638 	}
639 
640 	/* get the keyring at which to begin the search */
641 	keyring_ref = lookup_user_key(ringid, 0, KEY_SEARCH);
642 	if (IS_ERR(keyring_ref)) {
643 		ret = PTR_ERR(keyring_ref);
644 		goto error2;
645 	}
646 
647 	/* get the destination keyring if specified */
648 	dest_ref = NULL;
649 	if (destringid) {
650 		dest_ref = lookup_user_key(destringid, KEY_LOOKUP_CREATE,
651 					   KEY_WRITE);
652 		if (IS_ERR(dest_ref)) {
653 			ret = PTR_ERR(dest_ref);
654 			goto error3;
655 		}
656 	}
657 
658 	/* find the key type */
659 	ktype = key_type_lookup(type);
660 	if (IS_ERR(ktype)) {
661 		ret = PTR_ERR(ktype);
662 		goto error4;
663 	}
664 
665 	/* do the search */
666 	key_ref = keyring_search(keyring_ref, ktype, description);
667 	if (IS_ERR(key_ref)) {
668 		ret = PTR_ERR(key_ref);
669 
670 		/* treat lack or presence of a negative key the same */
671 		if (ret == -EAGAIN)
672 			ret = -ENOKEY;
673 		goto error5;
674 	}
675 
676 	/* link the resulting key to the destination keyring if we can */
677 	if (dest_ref) {
678 		ret = key_permission(key_ref, KEY_LINK);
679 		if (ret < 0)
680 			goto error6;
681 
682 		ret = key_link(key_ref_to_ptr(dest_ref), key_ref_to_ptr(key_ref));
683 		if (ret < 0)
684 			goto error6;
685 	}
686 
687 	ret = key_ref_to_ptr(key_ref)->serial;
688 
689 error6:
690 	key_ref_put(key_ref);
691 error5:
692 	key_type_put(ktype);
693 error4:
694 	key_ref_put(dest_ref);
695 error3:
696 	key_ref_put(keyring_ref);
697 error2:
698 	kfree(description);
699 error:
700 	return ret;
701 }
702 
703 /*
704  * Read a key's payload.
705  *
706  * The key must either grant the caller Read permission, or it must grant the
707  * caller Search permission when searched for from the process keyrings.
708  *
709  * If successful, we place up to buflen bytes of data into the buffer, if one
710  * is provided, and return the amount of data that is available in the key,
711  * irrespective of how much we copied into the buffer.
712  */
713 long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen)
714 {
715 	struct key *key;
716 	key_ref_t key_ref;
717 	long ret;
718 
719 	/* find the key first */
720 	key_ref = lookup_user_key(keyid, 0, 0);
721 	if (IS_ERR(key_ref)) {
722 		ret = -ENOKEY;
723 		goto error;
724 	}
725 
726 	key = key_ref_to_ptr(key_ref);
727 
728 	/* see if we can read it directly */
729 	ret = key_permission(key_ref, KEY_READ);
730 	if (ret == 0)
731 		goto can_read_key;
732 	if (ret != -EACCES)
733 		goto error;
734 
735 	/* we can't; see if it's searchable from this process's keyrings
736 	 * - we automatically take account of the fact that it may be
737 	 *   dangling off an instantiation key
738 	 */
739 	if (!is_key_possessed(key_ref)) {
740 		ret = -EACCES;
741 		goto error2;
742 	}
743 
744 	/* the key is probably readable - now try to read it */
745 can_read_key:
746 	ret = key_validate(key);
747 	if (ret == 0) {
748 		ret = -EOPNOTSUPP;
749 		if (key->type->read) {
750 			/* read the data with the semaphore held (since we
751 			 * might sleep) */
752 			down_read(&key->sem);
753 			ret = key->type->read(key, buffer, buflen);
754 			up_read(&key->sem);
755 		}
756 	}
757 
758 error2:
759 	key_put(key);
760 error:
761 	return ret;
762 }
763 
764 /*
765  * Change the ownership of a key
766  *
767  * The key must grant the caller Setattr permission for this to work, though
768  * the key need not be fully instantiated yet.  For the UID to be changed, or
769  * for the GID to be changed to a group the caller is not a member of, the
770  * caller must have sysadmin capability.  If either uid or gid is -1 then that
771  * attribute is not changed.
772  *
773  * If the UID is to be changed, the new user must have sufficient quota to
774  * accept the key.  The quota deduction will be removed from the old user to
775  * the new user should the attribute be changed.
776  *
777  * If successful, 0 will be returned.
778  */
779 long keyctl_chown_key(key_serial_t id, uid_t user, gid_t group)
780 {
781 	struct key_user *newowner, *zapowner = NULL;
782 	struct key *key;
783 	key_ref_t key_ref;
784 	long ret;
785 	kuid_t uid;
786 	kgid_t gid;
787 
788 	uid = make_kuid(current_user_ns(), user);
789 	gid = make_kgid(current_user_ns(), group);
790 	ret = -EINVAL;
791 	if ((user != (uid_t) -1) && !uid_valid(uid))
792 		goto error;
793 	if ((group != (gid_t) -1) && !gid_valid(gid))
794 		goto error;
795 
796 	ret = 0;
797 	if (user == (uid_t) -1 && group == (gid_t) -1)
798 		goto error;
799 
800 	key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
801 				  KEY_SETATTR);
802 	if (IS_ERR(key_ref)) {
803 		ret = PTR_ERR(key_ref);
804 		goto error;
805 	}
806 
807 	key = key_ref_to_ptr(key_ref);
808 
809 	/* make the changes with the locks held to prevent chown/chown races */
810 	ret = -EACCES;
811 	down_write(&key->sem);
812 
813 	if (!capable(CAP_SYS_ADMIN)) {
814 		/* only the sysadmin can chown a key to some other UID */
815 		if (user != (uid_t) -1 && !uid_eq(key->uid, uid))
816 			goto error_put;
817 
818 		/* only the sysadmin can set the key's GID to a group other
819 		 * than one of those that the current process subscribes to */
820 		if (group != (gid_t) -1 && !gid_eq(gid, key->gid) && !in_group_p(gid))
821 			goto error_put;
822 	}
823 
824 	/* change the UID */
825 	if (user != (uid_t) -1 && !uid_eq(uid, key->uid)) {
826 		ret = -ENOMEM;
827 		newowner = key_user_lookup(uid);
828 		if (!newowner)
829 			goto error_put;
830 
831 		/* transfer the quota burden to the new user */
832 		if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
833 			unsigned maxkeys = uid_eq(uid, GLOBAL_ROOT_UID) ?
834 				key_quota_root_maxkeys : key_quota_maxkeys;
835 			unsigned maxbytes = uid_eq(uid, GLOBAL_ROOT_UID) ?
836 				key_quota_root_maxbytes : key_quota_maxbytes;
837 
838 			spin_lock(&newowner->lock);
839 			if (newowner->qnkeys + 1 >= maxkeys ||
840 			    newowner->qnbytes + key->quotalen >= maxbytes ||
841 			    newowner->qnbytes + key->quotalen <
842 			    newowner->qnbytes)
843 				goto quota_overrun;
844 
845 			newowner->qnkeys++;
846 			newowner->qnbytes += key->quotalen;
847 			spin_unlock(&newowner->lock);
848 
849 			spin_lock(&key->user->lock);
850 			key->user->qnkeys--;
851 			key->user->qnbytes -= key->quotalen;
852 			spin_unlock(&key->user->lock);
853 		}
854 
855 		atomic_dec(&key->user->nkeys);
856 		atomic_inc(&newowner->nkeys);
857 
858 		if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
859 			atomic_dec(&key->user->nikeys);
860 			atomic_inc(&newowner->nikeys);
861 		}
862 
863 		zapowner = key->user;
864 		key->user = newowner;
865 		key->uid = uid;
866 	}
867 
868 	/* change the GID */
869 	if (group != (gid_t) -1)
870 		key->gid = gid;
871 
872 	ret = 0;
873 
874 error_put:
875 	up_write(&key->sem);
876 	key_put(key);
877 	if (zapowner)
878 		key_user_put(zapowner);
879 error:
880 	return ret;
881 
882 quota_overrun:
883 	spin_unlock(&newowner->lock);
884 	zapowner = newowner;
885 	ret = -EDQUOT;
886 	goto error_put;
887 }
888 
889 /*
890  * Change the permission mask on a key.
891  *
892  * The key must grant the caller Setattr permission for this to work, though
893  * the key need not be fully instantiated yet.  If the caller does not have
894  * sysadmin capability, it may only change the permission on keys that it owns.
895  */
896 long keyctl_setperm_key(key_serial_t id, key_perm_t perm)
897 {
898 	struct key *key;
899 	key_ref_t key_ref;
900 	long ret;
901 
902 	ret = -EINVAL;
903 	if (perm & ~(KEY_POS_ALL | KEY_USR_ALL | KEY_GRP_ALL | KEY_OTH_ALL))
904 		goto error;
905 
906 	key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
907 				  KEY_SETATTR);
908 	if (IS_ERR(key_ref)) {
909 		ret = PTR_ERR(key_ref);
910 		goto error;
911 	}
912 
913 	key = key_ref_to_ptr(key_ref);
914 
915 	/* make the changes with the locks held to prevent chown/chmod races */
916 	ret = -EACCES;
917 	down_write(&key->sem);
918 
919 	/* if we're not the sysadmin, we can only change a key that we own */
920 	if (capable(CAP_SYS_ADMIN) || uid_eq(key->uid, current_fsuid())) {
921 		key->perm = perm;
922 		ret = 0;
923 	}
924 
925 	up_write(&key->sem);
926 	key_put(key);
927 error:
928 	return ret;
929 }
930 
931 /*
932  * Get the destination keyring for instantiation and check that the caller has
933  * Write permission on it.
934  */
935 static long get_instantiation_keyring(key_serial_t ringid,
936 				      struct request_key_auth *rka,
937 				      struct key **_dest_keyring)
938 {
939 	key_ref_t dkref;
940 
941 	*_dest_keyring = NULL;
942 
943 	/* just return a NULL pointer if we weren't asked to make a link */
944 	if (ringid == 0)
945 		return 0;
946 
947 	/* if a specific keyring is nominated by ID, then use that */
948 	if (ringid > 0) {
949 		dkref = lookup_user_key(ringid, KEY_LOOKUP_CREATE, KEY_WRITE);
950 		if (IS_ERR(dkref))
951 			return PTR_ERR(dkref);
952 		*_dest_keyring = key_ref_to_ptr(dkref);
953 		return 0;
954 	}
955 
956 	if (ringid == KEY_SPEC_REQKEY_AUTH_KEY)
957 		return -EINVAL;
958 
959 	/* otherwise specify the destination keyring recorded in the
960 	 * authorisation key (any KEY_SPEC_*_KEYRING) */
961 	if (ringid >= KEY_SPEC_REQUESTOR_KEYRING) {
962 		*_dest_keyring = key_get(rka->dest_keyring);
963 		return 0;
964 	}
965 
966 	return -ENOKEY;
967 }
968 
969 /*
970  * Change the request_key authorisation key on the current process.
971  */
972 static int keyctl_change_reqkey_auth(struct key *key)
973 {
974 	struct cred *new;
975 
976 	new = prepare_creds();
977 	if (!new)
978 		return -ENOMEM;
979 
980 	key_put(new->request_key_auth);
981 	new->request_key_auth = key_get(key);
982 
983 	return commit_creds(new);
984 }
985 
986 /*
987  * Copy the iovec data from userspace
988  */
989 static long copy_from_user_iovec(void *buffer, const struct iovec *iov,
990 				 unsigned ioc)
991 {
992 	for (; ioc > 0; ioc--) {
993 		if (copy_from_user(buffer, iov->iov_base, iov->iov_len) != 0)
994 			return -EFAULT;
995 		buffer += iov->iov_len;
996 		iov++;
997 	}
998 	return 0;
999 }
1000 
1001 /*
1002  * Instantiate a key with the specified payload and link the key into the
1003  * destination keyring if one is given.
1004  *
1005  * The caller must have the appropriate instantiation permit set for this to
1006  * work (see keyctl_assume_authority).  No other permissions are required.
1007  *
1008  * If successful, 0 will be returned.
1009  */
1010 long keyctl_instantiate_key_common(key_serial_t id,
1011 				   const struct iovec *payload_iov,
1012 				   unsigned ioc,
1013 				   size_t plen,
1014 				   key_serial_t ringid)
1015 {
1016 	const struct cred *cred = current_cred();
1017 	struct request_key_auth *rka;
1018 	struct key *instkey, *dest_keyring;
1019 	void *payload;
1020 	long ret;
1021 	bool vm = false;
1022 
1023 	kenter("%d,,%zu,%d", id, plen, ringid);
1024 
1025 	ret = -EINVAL;
1026 	if (plen > 1024 * 1024 - 1)
1027 		goto error;
1028 
1029 	/* the appropriate instantiation authorisation key must have been
1030 	 * assumed before calling this */
1031 	ret = -EPERM;
1032 	instkey = cred->request_key_auth;
1033 	if (!instkey)
1034 		goto error;
1035 
1036 	rka = instkey->payload.data;
1037 	if (rka->target_key->serial != id)
1038 		goto error;
1039 
1040 	/* pull the payload in if one was supplied */
1041 	payload = NULL;
1042 
1043 	if (payload_iov) {
1044 		ret = -ENOMEM;
1045 		payload = kmalloc(plen, GFP_KERNEL);
1046 		if (!payload) {
1047 			if (plen <= PAGE_SIZE)
1048 				goto error;
1049 			vm = true;
1050 			payload = vmalloc(plen);
1051 			if (!payload)
1052 				goto error;
1053 		}
1054 
1055 		ret = copy_from_user_iovec(payload, payload_iov, ioc);
1056 		if (ret < 0)
1057 			goto error2;
1058 	}
1059 
1060 	/* find the destination keyring amongst those belonging to the
1061 	 * requesting task */
1062 	ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
1063 	if (ret < 0)
1064 		goto error2;
1065 
1066 	/* instantiate the key and link it into a keyring */
1067 	ret = key_instantiate_and_link(rka->target_key, payload, plen,
1068 				       dest_keyring, instkey);
1069 
1070 	key_put(dest_keyring);
1071 
1072 	/* discard the assumed authority if it's just been disabled by
1073 	 * instantiation of the key */
1074 	if (ret == 0)
1075 		keyctl_change_reqkey_auth(NULL);
1076 
1077 error2:
1078 	if (!vm)
1079 		kfree(payload);
1080 	else
1081 		vfree(payload);
1082 error:
1083 	return ret;
1084 }
1085 
1086 /*
1087  * Instantiate a key with the specified payload and link the key into the
1088  * destination keyring if one is given.
1089  *
1090  * The caller must have the appropriate instantiation permit set for this to
1091  * work (see keyctl_assume_authority).  No other permissions are required.
1092  *
1093  * If successful, 0 will be returned.
1094  */
1095 long keyctl_instantiate_key(key_serial_t id,
1096 			    const void __user *_payload,
1097 			    size_t plen,
1098 			    key_serial_t ringid)
1099 {
1100 	if (_payload && plen) {
1101 		struct iovec iov[1] = {
1102 			[0].iov_base = (void __user *)_payload,
1103 			[0].iov_len  = plen
1104 		};
1105 
1106 		return keyctl_instantiate_key_common(id, iov, 1, plen, ringid);
1107 	}
1108 
1109 	return keyctl_instantiate_key_common(id, NULL, 0, 0, ringid);
1110 }
1111 
1112 /*
1113  * Instantiate a key with the specified multipart payload and link the key into
1114  * the destination keyring if one is given.
1115  *
1116  * The caller must have the appropriate instantiation permit set for this to
1117  * work (see keyctl_assume_authority).  No other permissions are required.
1118  *
1119  * If successful, 0 will be returned.
1120  */
1121 long keyctl_instantiate_key_iov(key_serial_t id,
1122 				const struct iovec __user *_payload_iov,
1123 				unsigned ioc,
1124 				key_serial_t ringid)
1125 {
1126 	struct iovec iovstack[UIO_FASTIOV], *iov = iovstack;
1127 	long ret;
1128 
1129 	if (!_payload_iov || !ioc)
1130 		goto no_payload;
1131 
1132 	ret = rw_copy_check_uvector(WRITE, _payload_iov, ioc,
1133 				    ARRAY_SIZE(iovstack), iovstack, &iov);
1134 	if (ret < 0)
1135 		goto err;
1136 	if (ret == 0)
1137 		goto no_payload_free;
1138 
1139 	ret = keyctl_instantiate_key_common(id, iov, ioc, ret, ringid);
1140 err:
1141 	if (iov != iovstack)
1142 		kfree(iov);
1143 	return ret;
1144 
1145 no_payload_free:
1146 	if (iov != iovstack)
1147 		kfree(iov);
1148 no_payload:
1149 	return keyctl_instantiate_key_common(id, NULL, 0, 0, ringid);
1150 }
1151 
1152 /*
1153  * Negatively instantiate the key with the given timeout (in seconds) and link
1154  * the key into the destination keyring if one is given.
1155  *
1156  * The caller must have the appropriate instantiation permit set for this to
1157  * work (see keyctl_assume_authority).  No other permissions are required.
1158  *
1159  * The key and any links to the key will be automatically garbage collected
1160  * after the timeout expires.
1161  *
1162  * Negative keys are used to rate limit repeated request_key() calls by causing
1163  * them to return -ENOKEY until the negative key expires.
1164  *
1165  * If successful, 0 will be returned.
1166  */
1167 long keyctl_negate_key(key_serial_t id, unsigned timeout, key_serial_t ringid)
1168 {
1169 	return keyctl_reject_key(id, timeout, ENOKEY, ringid);
1170 }
1171 
1172 /*
1173  * Negatively instantiate the key with the given timeout (in seconds) and error
1174  * code and link the key into the destination keyring if one is given.
1175  *
1176  * The caller must have the appropriate instantiation permit set for this to
1177  * work (see keyctl_assume_authority).  No other permissions are required.
1178  *
1179  * The key and any links to the key will be automatically garbage collected
1180  * after the timeout expires.
1181  *
1182  * Negative keys are used to rate limit repeated request_key() calls by causing
1183  * them to return the specified error code until the negative key expires.
1184  *
1185  * If successful, 0 will be returned.
1186  */
1187 long keyctl_reject_key(key_serial_t id, unsigned timeout, unsigned error,
1188 		       key_serial_t ringid)
1189 {
1190 	const struct cred *cred = current_cred();
1191 	struct request_key_auth *rka;
1192 	struct key *instkey, *dest_keyring;
1193 	long ret;
1194 
1195 	kenter("%d,%u,%u,%d", id, timeout, error, ringid);
1196 
1197 	/* must be a valid error code and mustn't be a kernel special */
1198 	if (error <= 0 ||
1199 	    error >= MAX_ERRNO ||
1200 	    error == ERESTARTSYS ||
1201 	    error == ERESTARTNOINTR ||
1202 	    error == ERESTARTNOHAND ||
1203 	    error == ERESTART_RESTARTBLOCK)
1204 		return -EINVAL;
1205 
1206 	/* the appropriate instantiation authorisation key must have been
1207 	 * assumed before calling this */
1208 	ret = -EPERM;
1209 	instkey = cred->request_key_auth;
1210 	if (!instkey)
1211 		goto error;
1212 
1213 	rka = instkey->payload.data;
1214 	if (rka->target_key->serial != id)
1215 		goto error;
1216 
1217 	/* find the destination keyring if present (which must also be
1218 	 * writable) */
1219 	ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
1220 	if (ret < 0)
1221 		goto error;
1222 
1223 	/* instantiate the key and link it into a keyring */
1224 	ret = key_reject_and_link(rka->target_key, timeout, error,
1225 				  dest_keyring, instkey);
1226 
1227 	key_put(dest_keyring);
1228 
1229 	/* discard the assumed authority if it's just been disabled by
1230 	 * instantiation of the key */
1231 	if (ret == 0)
1232 		keyctl_change_reqkey_auth(NULL);
1233 
1234 error:
1235 	return ret;
1236 }
1237 
1238 /*
1239  * Read or set the default keyring in which request_key() will cache keys and
1240  * return the old setting.
1241  *
1242  * If a process keyring is specified then this will be created if it doesn't
1243  * yet exist.  The old setting will be returned if successful.
1244  */
1245 long keyctl_set_reqkey_keyring(int reqkey_defl)
1246 {
1247 	struct cred *new;
1248 	int ret, old_setting;
1249 
1250 	old_setting = current_cred_xxx(jit_keyring);
1251 
1252 	if (reqkey_defl == KEY_REQKEY_DEFL_NO_CHANGE)
1253 		return old_setting;
1254 
1255 	new = prepare_creds();
1256 	if (!new)
1257 		return -ENOMEM;
1258 
1259 	switch (reqkey_defl) {
1260 	case KEY_REQKEY_DEFL_THREAD_KEYRING:
1261 		ret = install_thread_keyring_to_cred(new);
1262 		if (ret < 0)
1263 			goto error;
1264 		goto set;
1265 
1266 	case KEY_REQKEY_DEFL_PROCESS_KEYRING:
1267 		ret = install_process_keyring_to_cred(new);
1268 		if (ret < 0) {
1269 			if (ret != -EEXIST)
1270 				goto error;
1271 			ret = 0;
1272 		}
1273 		goto set;
1274 
1275 	case KEY_REQKEY_DEFL_DEFAULT:
1276 	case KEY_REQKEY_DEFL_SESSION_KEYRING:
1277 	case KEY_REQKEY_DEFL_USER_KEYRING:
1278 	case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
1279 	case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
1280 		goto set;
1281 
1282 	case KEY_REQKEY_DEFL_NO_CHANGE:
1283 	case KEY_REQKEY_DEFL_GROUP_KEYRING:
1284 	default:
1285 		ret = -EINVAL;
1286 		goto error;
1287 	}
1288 
1289 set:
1290 	new->jit_keyring = reqkey_defl;
1291 	commit_creds(new);
1292 	return old_setting;
1293 error:
1294 	abort_creds(new);
1295 	return ret;
1296 }
1297 
1298 /*
1299  * Set or clear the timeout on a key.
1300  *
1301  * Either the key must grant the caller Setattr permission or else the caller
1302  * must hold an instantiation authorisation token for the key.
1303  *
1304  * The timeout is either 0 to clear the timeout, or a number of seconds from
1305  * the current time.  The key and any links to the key will be automatically
1306  * garbage collected after the timeout expires.
1307  *
1308  * If successful, 0 is returned.
1309  */
1310 long keyctl_set_timeout(key_serial_t id, unsigned timeout)
1311 {
1312 	struct key *key, *instkey;
1313 	key_ref_t key_ref;
1314 	long ret;
1315 
1316 	key_ref = lookup_user_key(id, KEY_LOOKUP_CREATE | KEY_LOOKUP_PARTIAL,
1317 				  KEY_SETATTR);
1318 	if (IS_ERR(key_ref)) {
1319 		/* setting the timeout on a key under construction is permitted
1320 		 * if we have the authorisation token handy */
1321 		if (PTR_ERR(key_ref) == -EACCES) {
1322 			instkey = key_get_instantiation_authkey(id);
1323 			if (!IS_ERR(instkey)) {
1324 				key_put(instkey);
1325 				key_ref = lookup_user_key(id,
1326 							  KEY_LOOKUP_PARTIAL,
1327 							  0);
1328 				if (!IS_ERR(key_ref))
1329 					goto okay;
1330 			}
1331 		}
1332 
1333 		ret = PTR_ERR(key_ref);
1334 		goto error;
1335 	}
1336 
1337 okay:
1338 	key = key_ref_to_ptr(key_ref);
1339 	key_set_timeout(key, timeout);
1340 	key_put(key);
1341 
1342 	ret = 0;
1343 error:
1344 	return ret;
1345 }
1346 
1347 /*
1348  * Assume (or clear) the authority to instantiate the specified key.
1349  *
1350  * This sets the authoritative token currently in force for key instantiation.
1351  * This must be done for a key to be instantiated.  It has the effect of making
1352  * available all the keys from the caller of the request_key() that created a
1353  * key to request_key() calls made by the caller of this function.
1354  *
1355  * The caller must have the instantiation key in their process keyrings with a
1356  * Search permission grant available to the caller.
1357  *
1358  * If the ID given is 0, then the setting will be cleared and 0 returned.
1359  *
1360  * If the ID given has a matching an authorisation key, then that key will be
1361  * set and its ID will be returned.  The authorisation key can be read to get
1362  * the callout information passed to request_key().
1363  */
1364 long keyctl_assume_authority(key_serial_t id)
1365 {
1366 	struct key *authkey;
1367 	long ret;
1368 
1369 	/* special key IDs aren't permitted */
1370 	ret = -EINVAL;
1371 	if (id < 0)
1372 		goto error;
1373 
1374 	/* we divest ourselves of authority if given an ID of 0 */
1375 	if (id == 0) {
1376 		ret = keyctl_change_reqkey_auth(NULL);
1377 		goto error;
1378 	}
1379 
1380 	/* attempt to assume the authority temporarily granted to us whilst we
1381 	 * instantiate the specified key
1382 	 * - the authorisation key must be in the current task's keyrings
1383 	 *   somewhere
1384 	 */
1385 	authkey = key_get_instantiation_authkey(id);
1386 	if (IS_ERR(authkey)) {
1387 		ret = PTR_ERR(authkey);
1388 		goto error;
1389 	}
1390 
1391 	ret = keyctl_change_reqkey_auth(authkey);
1392 	if (ret < 0)
1393 		goto error;
1394 	key_put(authkey);
1395 
1396 	ret = authkey->serial;
1397 error:
1398 	return ret;
1399 }
1400 
1401 /*
1402  * Get a key's the LSM security label.
1403  *
1404  * The key must grant the caller View permission for this to work.
1405  *
1406  * If there's a buffer, then up to buflen bytes of data will be placed into it.
1407  *
1408  * If successful, the amount of information available will be returned,
1409  * irrespective of how much was copied (including the terminal NUL).
1410  */
1411 long keyctl_get_security(key_serial_t keyid,
1412 			 char __user *buffer,
1413 			 size_t buflen)
1414 {
1415 	struct key *key, *instkey;
1416 	key_ref_t key_ref;
1417 	char *context;
1418 	long ret;
1419 
1420 	key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, KEY_VIEW);
1421 	if (IS_ERR(key_ref)) {
1422 		if (PTR_ERR(key_ref) != -EACCES)
1423 			return PTR_ERR(key_ref);
1424 
1425 		/* viewing a key under construction is also permitted if we
1426 		 * have the authorisation token handy */
1427 		instkey = key_get_instantiation_authkey(keyid);
1428 		if (IS_ERR(instkey))
1429 			return PTR_ERR(instkey);
1430 		key_put(instkey);
1431 
1432 		key_ref = lookup_user_key(keyid, KEY_LOOKUP_PARTIAL, 0);
1433 		if (IS_ERR(key_ref))
1434 			return PTR_ERR(key_ref);
1435 	}
1436 
1437 	key = key_ref_to_ptr(key_ref);
1438 	ret = security_key_getsecurity(key, &context);
1439 	if (ret == 0) {
1440 		/* if no information was returned, give userspace an empty
1441 		 * string */
1442 		ret = 1;
1443 		if (buffer && buflen > 0 &&
1444 		    copy_to_user(buffer, "", 1) != 0)
1445 			ret = -EFAULT;
1446 	} else if (ret > 0) {
1447 		/* return as much data as there's room for */
1448 		if (buffer && buflen > 0) {
1449 			if (buflen > ret)
1450 				buflen = ret;
1451 
1452 			if (copy_to_user(buffer, context, buflen) != 0)
1453 				ret = -EFAULT;
1454 		}
1455 
1456 		kfree(context);
1457 	}
1458 
1459 	key_ref_put(key_ref);
1460 	return ret;
1461 }
1462 
1463 /*
1464  * Attempt to install the calling process's session keyring on the process's
1465  * parent process.
1466  *
1467  * The keyring must exist and must grant the caller LINK permission, and the
1468  * parent process must be single-threaded and must have the same effective
1469  * ownership as this process and mustn't be SUID/SGID.
1470  *
1471  * The keyring will be emplaced on the parent when it next resumes userspace.
1472  *
1473  * If successful, 0 will be returned.
1474  */
1475 long keyctl_session_to_parent(void)
1476 {
1477 	struct task_struct *me, *parent;
1478 	const struct cred *mycred, *pcred;
1479 	struct callback_head *newwork, *oldwork;
1480 	key_ref_t keyring_r;
1481 	struct cred *cred;
1482 	int ret;
1483 
1484 	keyring_r = lookup_user_key(KEY_SPEC_SESSION_KEYRING, 0, KEY_LINK);
1485 	if (IS_ERR(keyring_r))
1486 		return PTR_ERR(keyring_r);
1487 
1488 	ret = -ENOMEM;
1489 
1490 	/* our parent is going to need a new cred struct, a new tgcred struct
1491 	 * and new security data, so we allocate them here to prevent ENOMEM in
1492 	 * our parent */
1493 	cred = cred_alloc_blank();
1494 	if (!cred)
1495 		goto error_keyring;
1496 	newwork = &cred->rcu;
1497 
1498 	cred->session_keyring = key_ref_to_ptr(keyring_r);
1499 	keyring_r = NULL;
1500 	init_task_work(newwork, key_change_session_keyring);
1501 
1502 	me = current;
1503 	rcu_read_lock();
1504 	write_lock_irq(&tasklist_lock);
1505 
1506 	ret = -EPERM;
1507 	oldwork = NULL;
1508 	parent = me->real_parent;
1509 
1510 	/* the parent mustn't be init and mustn't be a kernel thread */
1511 	if (parent->pid <= 1 || !parent->mm)
1512 		goto unlock;
1513 
1514 	/* the parent must be single threaded */
1515 	if (!thread_group_empty(parent))
1516 		goto unlock;
1517 
1518 	/* the parent and the child must have different session keyrings or
1519 	 * there's no point */
1520 	mycred = current_cred();
1521 	pcred = __task_cred(parent);
1522 	if (mycred == pcred ||
1523 	    mycred->session_keyring == pcred->session_keyring) {
1524 		ret = 0;
1525 		goto unlock;
1526 	}
1527 
1528 	/* the parent must have the same effective ownership and mustn't be
1529 	 * SUID/SGID */
1530 	if (!uid_eq(pcred->uid,	 mycred->euid) ||
1531 	    !uid_eq(pcred->euid, mycred->euid) ||
1532 	    !uid_eq(pcred->suid, mycred->euid) ||
1533 	    !gid_eq(pcred->gid,	 mycred->egid) ||
1534 	    !gid_eq(pcred->egid, mycred->egid) ||
1535 	    !gid_eq(pcred->sgid, mycred->egid))
1536 		goto unlock;
1537 
1538 	/* the keyrings must have the same UID */
1539 	if ((pcred->session_keyring &&
1540 	     !uid_eq(pcred->session_keyring->uid, mycred->euid)) ||
1541 	    !uid_eq(mycred->session_keyring->uid, mycred->euid))
1542 		goto unlock;
1543 
1544 	/* cancel an already pending keyring replacement */
1545 	oldwork = task_work_cancel(parent, key_change_session_keyring);
1546 
1547 	/* the replacement session keyring is applied just prior to userspace
1548 	 * restarting */
1549 	ret = task_work_add(parent, newwork, true);
1550 	if (!ret)
1551 		newwork = NULL;
1552 unlock:
1553 	write_unlock_irq(&tasklist_lock);
1554 	rcu_read_unlock();
1555 	if (oldwork)
1556 		put_cred(container_of(oldwork, struct cred, rcu));
1557 	if (newwork)
1558 		put_cred(cred);
1559 	return ret;
1560 
1561 error_keyring:
1562 	key_ref_put(keyring_r);
1563 	return ret;
1564 }
1565 
1566 /*
1567  * The key control system call
1568  */
1569 SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
1570 		unsigned long, arg4, unsigned long, arg5)
1571 {
1572 	switch (option) {
1573 	case KEYCTL_GET_KEYRING_ID:
1574 		return keyctl_get_keyring_ID((key_serial_t) arg2,
1575 					     (int) arg3);
1576 
1577 	case KEYCTL_JOIN_SESSION_KEYRING:
1578 		return keyctl_join_session_keyring((const char __user *) arg2);
1579 
1580 	case KEYCTL_UPDATE:
1581 		return keyctl_update_key((key_serial_t) arg2,
1582 					 (const void __user *) arg3,
1583 					 (size_t) arg4);
1584 
1585 	case KEYCTL_REVOKE:
1586 		return keyctl_revoke_key((key_serial_t) arg2);
1587 
1588 	case KEYCTL_DESCRIBE:
1589 		return keyctl_describe_key((key_serial_t) arg2,
1590 					   (char __user *) arg3,
1591 					   (unsigned) arg4);
1592 
1593 	case KEYCTL_CLEAR:
1594 		return keyctl_keyring_clear((key_serial_t) arg2);
1595 
1596 	case KEYCTL_LINK:
1597 		return keyctl_keyring_link((key_serial_t) arg2,
1598 					   (key_serial_t) arg3);
1599 
1600 	case KEYCTL_UNLINK:
1601 		return keyctl_keyring_unlink((key_serial_t) arg2,
1602 					     (key_serial_t) arg3);
1603 
1604 	case KEYCTL_SEARCH:
1605 		return keyctl_keyring_search((key_serial_t) arg2,
1606 					     (const char __user *) arg3,
1607 					     (const char __user *) arg4,
1608 					     (key_serial_t) arg5);
1609 
1610 	case KEYCTL_READ:
1611 		return keyctl_read_key((key_serial_t) arg2,
1612 				       (char __user *) arg3,
1613 				       (size_t) arg4);
1614 
1615 	case KEYCTL_CHOWN:
1616 		return keyctl_chown_key((key_serial_t) arg2,
1617 					(uid_t) arg3,
1618 					(gid_t) arg4);
1619 
1620 	case KEYCTL_SETPERM:
1621 		return keyctl_setperm_key((key_serial_t) arg2,
1622 					  (key_perm_t) arg3);
1623 
1624 	case KEYCTL_INSTANTIATE:
1625 		return keyctl_instantiate_key((key_serial_t) arg2,
1626 					      (const void __user *) arg3,
1627 					      (size_t) arg4,
1628 					      (key_serial_t) arg5);
1629 
1630 	case KEYCTL_NEGATE:
1631 		return keyctl_negate_key((key_serial_t) arg2,
1632 					 (unsigned) arg3,
1633 					 (key_serial_t) arg4);
1634 
1635 	case KEYCTL_SET_REQKEY_KEYRING:
1636 		return keyctl_set_reqkey_keyring(arg2);
1637 
1638 	case KEYCTL_SET_TIMEOUT:
1639 		return keyctl_set_timeout((key_serial_t) arg2,
1640 					  (unsigned) arg3);
1641 
1642 	case KEYCTL_ASSUME_AUTHORITY:
1643 		return keyctl_assume_authority((key_serial_t) arg2);
1644 
1645 	case KEYCTL_GET_SECURITY:
1646 		return keyctl_get_security((key_serial_t) arg2,
1647 					   (char __user *) arg3,
1648 					   (size_t) arg4);
1649 
1650 	case KEYCTL_SESSION_TO_PARENT:
1651 		return keyctl_session_to_parent();
1652 
1653 	case KEYCTL_REJECT:
1654 		return keyctl_reject_key((key_serial_t) arg2,
1655 					 (unsigned) arg3,
1656 					 (unsigned) arg4,
1657 					 (key_serial_t) arg5);
1658 
1659 	case KEYCTL_INSTANTIATE_IOV:
1660 		return keyctl_instantiate_key_iov(
1661 			(key_serial_t) arg2,
1662 			(const struct iovec __user *) arg3,
1663 			(unsigned) arg4,
1664 			(key_serial_t) arg5);
1665 
1666 	case KEYCTL_INVALIDATE:
1667 		return keyctl_invalidate_key((key_serial_t) arg2);
1668 
1669 	default:
1670 		return -EOPNOTSUPP;
1671 	}
1672 }
1673